Method of making copying paper



Nov. 10, 1970 sumo OTANI EI'AL 3,539,376

METHOD OF MAKING COPYING PAPER Filed Jan. 24, 1968 United States Patent 3,539,376 METHOD OF MAKING COPYING PAPER Sumio Otani, Yao, and Yasugi Shimada, Hirakata, Japan, assignors to Carbon Paper Co., Ltd, Osaka, Japan Filed Jan. 24, 1968, Ser. No. 700,161 Claims priority, application Japan, Jan. 28, 1967, 42/ 5,725 Int. Cl. B41111 5/10 US. Cl. 117-364 3 Claims ABSTRACT OF THE DISCLOSURE Copying paper comprises a record pigment layer, a covering layer and an adhesive layer. Said record pigment layer is formed on the back surface of paper by applying coating materials comprising vinyl resin record pigment, oil and fat or waxy compound, dispersant and solvent, and thereafter evaporating said solvent. Said covering layer is formed on said record pigment layer by applying coating materials comprising cellulose derivatives or synthetic resin, pigment, waxy compound and solvent, and then evaporating said solvent. Said adhesive layer is provided on said covering layer by applying coating materials comprising low molecular polyethylene, a waxy compound and solvent, and then evaporating said solvent.

This invention relates to copying paper which is capable of making several copies at a time without using carbon paper and more particularly to copying paper having a construction in which the back surface of the sheet is coated with transfer record materials, said copying paper being characterized by such features: the layer of said transfer record materials is formed of three layers; the color of the exterior surface of said transfer record material layers is the same as that of the base sheet or white; and said copying paper is free from smudging the fingers, clothes or other papers which are brought into contact therewith during handling.

Various types of copying paper having transfer materials applied on the back face thereof and capable of making several copies at a time have hitherto been invented, and particularly, so-called carbonized copying paper has extensively been used, the transfer coating materials of said carbonized copying paper being of carbon ink type comprising wax, oil and fat, and coloring materials. These types of copying paper, however, have a defect of smudging fingers and papers brought into contact with the transfer materials, so that various studies to overcome the disadvantage have been made. For instance, a resin is added to the coating materials of carbon ink type to reduce staining, or, in an attempt to prevent smudging, a synthetic resin, wax or waxy compound, oil and fat, and coloring material dissolved and dispersed in solvent are applied to effect the microscopically discrete deposit of waxy compound formed on the surface of the coating materials upon evaporation of the solvent.

By the present inventors, the smudge-free effect had previously been secured by copying paper in which a discontinuous adhesive layer consisting of low molecular weight polyethylene and waxy compound is formed over the surface of a colored layer comprising synthetic resin and color pigment. These types of copying paper have come into use in place of carbonized copying paper. However, these copying sheets have the coated copying layer on the back surface thereof colored in the dark color of the record color itself, and the back surface is colored dark, so that the user still feels uneasy for possible staining. With respect to the commercial value this is also disadvantage. Therefore, it has been desired to have copying paper which has the same appearance as ordinary paper and which is capable of copying without using carbon ice paper. The main object of the present invention is to obtain such copying paper.

The present invention will be more easily understood from a reading of the following description and by reference to the accompanying drawings in which:

FIG. 1 is a cross-sectional view of copying paper according to the invention; and

FIG. 2 is a cross-sectional view illustrating the same when pen or typewriter pressure is applied thereon.

Referring to the accompanying drawings, FIG. 1 shows copying paper of the present invention having a structure wherein the back surface of a base sheet 2 is covered with a microscopically discrete record pigment layer 3, said layer 3 being covered with a microscopically discrete covering layer 4, said layer 4 being covered with a microscopically discrete adhesive layer 5. In use, as shown in FIG. 2, sheets of the copying paper are piled on a sheet of paper and when a writing instrument or typewriter performs recording thereon, the portions of three layers directly pressed by said means are adhered and transferred to the surface of the underlying sheet 1 by the action of the adhesive layer 5. The top surface of the adhered and transferred materials, as illustrated in FIG. 2, clearly shows the impression with a darker colored record pigment layer 3.

As apparent herein, the copying paper of the present invention has a record pigment layer therein, the surface of said layer being covered with a covering layer and an adhesive layer, said covering layer being in white color or in the same color as the base sheet. Thus, it is devised to provide the copying paper with the same appearance as the ordinary paper.

The present structure is obtained by interposing a covering layer (of white or similar color to base sheet) between the colored layer and the adhesive layer of the former invention by the present inventors. With respect to the structure, copying paper having a construction similar to such structure is already known.

In the US. Pat. No. 2,729,575 is disclosed a transfer sheet with a structure wherein the front face of a base sheet is covered with a coating of a pressure sensitive wax carbon ink type including a dye, said coating being covered with a resin coating provided by first dissolving a resinous film-forming substance in a solvent which is a non-solvent for said dye and then applying and drying the same, said resin coating being covered with a wax layer which is applied in molten form and thereafter cooled. In this case, in an attempt to cover the coating of carbon ink type by resin coating aluminum powder is also added to the resin coating. The present inventors also attempted to manufacture the copying paper having a structure comprising a carbon ink layer provided on the back surface of a sheet and a protective coating layer formed over said layer, or various cases have been studied as to a protective coating layer formed of wax and pigment. As a result of various studies conducted, copying paper of the present invention is now invented, in which interrelatedly multiplied effects are brought about by its structure, each composition and condition for the formation of the three coating layers, and the combination thereof.

While several embodiments and the detailed description of the invention are set forth as follows, it is to be understood that they are given only by way of example and that the invention is not limited thereto.

EXAMPLE 1 An ink composition of a microscopically discrete record pigment layer having the following components is applied to the back surface of a white sheet 2 by an ordinary coating means and is then dried by evaporating the solvent to obtain a microscopically discrete record pigment layer 3. The ink composition is prepared by first dissolving the resin in the solvent in a ball-mill, then adding the rest of the ingredients and kneading the mixture for 8 hours.

INK COMPOSITION OF MIOROSCOPICALLY DISCRETE RECORD PIGMENT LAYER Parts by weight Record pigment Iron blue 0.2 Phthalocyanine violet O. 02 Titanium dioxide 0.5 Calcium carbonate" 5.

Oil and fat or waxy com- Castor oil 0. 2

poun Dispersant Anionic surface active agent- 0. 08

Synthetic resin Vinyl chloride Vinyl acetate eopolymer O. 4 Maleic acid Solvent Methyl ethyl ketone 2. O Toluene 6. 5

1 Eg. Vinylitc VMCH (trademark).

As for the record pigment, iron blue, carbon black, ultramarine, phthalocyanine pigment, fanal color, alkali blue and the like are used alone or in combination. A white pigment such as titanium dioxide or zinc dioxide is normally mixed with extender such as calcium carbonate, barium sulfate, clay or talc. These pigments, together with the oil and fat or waxy compound and dispersant which are contained in the ink composition, are used in such quantity as to form said record pigment layer into porous or microscopically discrete structure.

Castor oil, lanolin, hardened oil, wax, stearic acid, palmitic acid and the like are used alone or in combination for the oil and fat or waxy compound, provided that said substances and the resin used are insoluble in each other and that the former are soluble in the solvent used.

For the dispersant, nonionic, anionic, cationic surface active agent, or synthetic resin having protective colloid action is employed depending upon the pigment used. As mentioned above, since the ink composition comprises a relatively small amount of synthetic resin, a relatively large amount of pigments, a suitable amount of waxy compound and solvent, it is strictly required that the pigments be dispersed uniformly without precipitation and that the condition and viscosity of the ink composition be kept uniform in order to secure the uniform application of said ink composition over the base sheet. The dispersant must accordingly be added in a suitable quantity.

The most suitable resin as the synthetic resin in the present invention is the copolymer of vinyl chloride such as a copolymer of vinyl chloride vinyl acetate, a copolymer of vinyl chloride-vinyl acetate maleic acid, or a copolymer of vinyl chloride-vinyl acetate vinyl alcohol. However, it needs not be limited to said resin but any synthetic resin which is insoluble in a solvent in the ink composition of the microscopically discrete covering layer may also be used so long as it is of such resins, having film forming ability, to form a porous or microscopically discrete coating by oil and fat or waxy compound and pigments in the composition, and having high exfoliation. The microscopically discrete record pigment layer is provided with a specific property, whereby, while no transference thereof being effected in normal condition, only to the sheet coated with an adhesive substance such as wax, the pressed portion of said layer is transferred under the pressure applied with a pen or typewriter.

Next, over the surface of the record pigment layer 3 an ink composition of a covering layer which is microscopically discrete and to be adhered to said layer 3 is coated, and then dried for the evaporation of the solvent, whereby a microscopically discrete white covering layer 4 is formed. To prepare the ink composition, polyethylone is heated and dissolved in toluene, which is thereafter mixed with a butyral resin dissolved in methanol, and the mixture thus obtained and titanium white are mixed in a ball-mill for 8 hours.

INK COMPOSITION OF MICROSOOI-ICALLY DISCRETE COVERING LAYER Resin is to be soluble in an alcoholic solvent but insoluble in a hydrocarbon solvent. Resin such as butyral resin, nitrocellulose, polyvinylpyrrolidone or phenol resin is most suitable for the synthetic resin in said covering layer of the present invention. It is not particularly limited to such a resin but any resin which is insoluble in the solvent of the ink composition of a microscopically discrete adhesive layer to be coated over said covering layer may also be used. For the pigment, since the base sheet is generally white, it is a normal practice to use a white pigment such as titanium dioxide, zinc dioxide or lithopon. Without departing from the spirit of the invention, an extender such as calcium carbonate may be mixed therewith, or, a small quantity of pink pigment may be added thereto when the base sheet is pink and a green pigment when it is dark green thereby making the front and rear surfaces of the sheet appear the same color.

For the waxy compound, low molecular weight polyethylene, ceresine, hardened oil, carnauba wax, paraflin, stearic acid or the like is found suitable, and particularly low molecular weight polyethylene or parafiin of high melting point has created a satisfactory result. Strange to say, when an ink composition without such a waxy compound was applied, it was found out that the copying ability was seriously impaired or that only the adhesive and covering layers were exfoliated without the simultaneous exfoliation of microscopically discrete record pigment layer, and as a result no impression was produced. A suitable amount of waxy compound was thus found to be an essential component of the microscopically discrete white covering layer.

As the last step, an ink composition of a microscopically discrete adhesive layer described below is coated on the microscopically discrete white covering layer 4 and is then dried to form a microscopically discrete adhesive layer 5, whereby a copying paper with white back and front surfaces in accordance with the present invention is obtained. To prepare the ink composition, low molecular Weight polyethylene and powdered stearic acid of the components are heated and dissolved at a temperature of 82 C. in 4 parts by weight of Pegasol Arcwhile being stirred, and when completely disolved the heat is removed and the rest of Unisol is added.

INK COMPOSITION OF MICROSCUPICALLY DISCRETE ADHESIVE LAYER 1 Trademark, manufactured by Eastman Chemical Products, Inc. 2 Trademark, manufactured by Mobil Oil 00.

Good results have been obtained using low molecular weight polyethylene having average molecular weight of approximttely between 1,500 and 3,000 such as, for example, A-C Polyethylene manufactured by Allied Chemical Corp., A-Wax by BASF, Epolene N or LV by Eastman Chemical Products, Inc. or Sun Wax by Sanyo Chemical Industry Co., Ltd.

For the waxy compound, it is suitable to use a waxy substance such as paraffin, ceresine, stearic acid or thardened oil which is readily disolved in the solvent employed and the major portion of which, even when cooled, remain still in dissolved condition.

For the solvent used in the invention, hydrocarbon solvent is ideal. Particularly good results have been obtained using a combination of aromatic hydrocarbons and aliphatic hydrocarbons as, for example, a combination of toluene and petroleum benzine, and among those on sale, as Pegasol Aro-80, a product of Mobil Oil Co. (consisting of 72-76% aromatic hydrocarbons and 2428% aliphatic hydrocarbons, and having dry point of 123 C.), or Unisol of Fuji Iron & Steel Co. (consisting of 58% aromatic hydrocarbons and 42% aliphatic hydrocarbons, and having dry point 150 C.). Needless to say, the copying paper can be made of only aromatic hydrocarbons as toluene or aliphatic hydrocarbons like benzine, in which case proper attention should be given to the temperature of the ink composition, or a suitable resin should be added.

This is due to the fact that in case where only aromatic hydrocarbons are used, polyethylene is not readily crystallized because of the low aniline point of said solvent and the crystals obtained are not readily formed into uniform particles, while the ink composition is provided with high viscosity thereby the formation of ink with high concentration being made difficult. Therefore, when aliphatic hydrocarbons are added to raise the aniline points, polyethylene crystals are formed in uniformity, which facilitates the formation of ink having low viscosity but high concentration, while the difference in solubility parameter created between the said adhesive layer and the underlying layer makes it difiicult to dissolve said underlying layer and good results are thus accomplished in achieving the uniformity of quality.

EXAMPLE 2 On the rear surface of a light pink sheet of paper 2, an ink composition of a microscopically discrete record pigment layer described below is applied and then dried for evaporation of the solvent, whereby a microscopically discrete record pigment layer 3 is provided. Next, over the said layer 3 an ink composition of a microscopically discrete covering layer is applied and dried, whereby a microscopically discrete covering layer 4 is provided to cover the underlying said pigment layer. Further, over the said layer 4 an ink composition of a microscopically discrete adhesive layer having the composition stated below is applied and dried for evaporation of the solvent, whereby a microscopically discrete adhesive layer 5 is formed. In this way, copying paper in accordance with the present invention having a front surface lightly colored in pink and a white rear surface is obtained. In preparing each ink composition the above procedure of Example 1 18 repeated.

OlIPOSIIION OF MIOROSCOPICALLY DISCRETE INK c 1 RECORD PIGMENT LAYER 1 Eg. Vinylite VAGH (trademark).

INK COMPOSITION OF MICROSCOPICALLY DISCRETE COVERING LAYER Parts by weight Synthetic resin. Nitrocellulose 0. 2 Pigment Titanium dioxide. 4. 5 Low molecular weight Low molecular weight polyethylene. 0. 2

polyethylene or waxy compound.

Solvent Met'n'mol 7.0 Toluene 1v 0 1 Trademark, manufactured by Sanyo Chemical Industry 00., Ltd. 2 Trademark, manufactured by Fuji Iron dz Steel Co.

EXAMPLE 3 As in Examples 1 and 2 an ink composition for each layer comprising the below described ingredients is applied to a sheet to form the three layers, whereby the copying paper of the present invention is obtained. In case of this example, light blue paper is used as a base sheet, and by coloring the microscopically discrete covering layer thereon in light blue color, copying paper having the front and back surfaces thereof colored in the same light blue color in accordance with present invention is produced. The process for preparing each ink composition is the same as that in Example 1.

INK COMPOSITION OF MICROSCOPICALLY DISCRETE RECORD PIGMENT LAYER INK COMPOSITION OF MICROSCOPICALLY DISCRETE COVERING LAYER Parts by weight Synthetic resin Polyvinylpyrrolidone O. 2

Pigment Titanium dioxide 4. 4

Iron blue- 0. 02

Low molecular weight Paraffin 0. 1

polyethylene or Low molecular weight polyethylene. 0. 1 waxy compound.

Solvent Methanol 7. 0

Toluene 1. 0

INK COMPOSITION OF MICROSCOPICALLY DISCRETE ADHESIVE LAYER Parts by weight Low molecular Weight polyethylene. A-C polyethylene 2. 0 Waxy compound. Paralfin 0. 2

Hydrocarbon solvent Toluene 25. 0

Petroleum benzine- 10. 0

1 Allied Chemical Corp.

What we claim is:

1. A method of making copying paper comprising the steps of forming a record pigment layer of a record pigment and a vinyl resin on the back surface of paper by applying a coating colution thereon and evaporating a solvent contained therein, said coating solution being prepared by dissolving and dispersing in a solvent materials including a vinyl resin, at pigment as record pigment, a substance selected from the group consisting of oil and fat and waxy compound which is immiscible for said vinyl resin, nonvolatile and non-drying, and a dispersant for said pigment,

applying a covering layer on the record pigment layer by applying a covering solution and evaporating a solvent contained therein, said covering solution being prepared by dissolving and dispersing in a solvent materials including a substance selected from the group consisting of cellulose derivatives, :1 pigment selected from the group consisting of a white pigment and a pigment of the same color as said paper, and a waxy compound, said solvent being a non-solvent for the vinyl resin and the igment forming said underlying record pigment layer but a solvent for said synthetic resin and said waxy compound,

applying a microscopically discrete transparent adhesive layer on the covering layer by applying an adhesive-providing solution and evaporating a solvent contained therein, said adhesive-providing solution being prepared by dissolving and dispersing low molecular polyethylene, a waxy compound selected from the group consisting of stearic acid and parafiin in a mixed solvent of aromatic hydrocarbons and aliphatic hydrocarbons, wherein the ink composition of said microscopically discrete record pigment layer and wherein the ink composition of said microscopically discrete covering layer comprises:

Parts by Weight Synthetic resin Butyra-l resin 0. 4 Pigment Titanium dioxide. 4. Waxy compound Polyethylene" 0. 2

Solvent Toluene 1. 0 Methanol 7, O

and wherein the ink composition of said microscopically discrete adhesive layer comprises:

Parts by weight Low molecular weight 1, 2

polyethylene.

Waxy compound Stearic acid 0. G

Hydrocarbon solvent l2. 0

2. A method of making copying paper comprising the steps of forming a record pigment layer of a record pigment and a vinyl resin on the back surface of paper by applying a coating solution thereon and evaporating a solvent contained therein, said coating solution being prepared by dissolving and dispersing in a solvent materials including a vinyl resin, a igment, a substance selected from the group consisting of oil and fat and waxy compound which is immiscible for said vinyl resin, nonvolatile and non-drying, and a dispersant for said pigment,

applying a covering layer on the record pigment layer by applying a covering solution and evaporating a solvent contained therein, said covering solution being prepared by dissolving and dispersing in a solvent materials including a substance selected from the group consisting of cellulose derivatives, a pigment selected from the group consisting of a white pigment and a pigment of the same color as said paper, and a Waxy compound, said solvent being a non-solvent for the vinyl resin and the pigment forming said underlying record pigment layer but a solvent for said synthetic resin and said waxy compound,

applying a microscopically discrete transparent adhesive layer on the covering layer by applying an adhesive- 8 providing solution and evaporating a solvent contained therein, said adhesive-providing solution being prepared by dissolving and dispersing low molecular polyethylene, a waxy compound selected from the group consisting of stearic acid and paraifin in a mixed solvent of aromatic hydrocarbons and aliphatic hydrocarbons, wherein the ink composition of said microscopically discrete record pigment layer comand wherein the ink composition of said microscopically discrete covering layer comprises:

Parts by weight Synthetic 1'esin.. Nitrocellulose 0. 2 Titanium dioxide 4, 5

Waxy compound.- Low molecular weight polyethylene. 0, 2

Solvent Methanol 7, 0 Toluene 1: 0

and wherein the ink composition of said microscoph cally discrete adhesive layer comprises:

Parts by weight Low molecular weight polyethylene 1. 0 Waxy compound Stcaric acid... 0. 2 Hydrocarbon solvent- 10, 0

3. A method of making copying paper comprising the steps of forming a record pigment layer of a record pigment and a vinyl resin on the back surface of paper by applying a coating solution thereon and evaporating a solvent contained therein, said coating solution being prepared by dissolving and dispersing in a solvent materials including a vinyl resin, a pig-ment as record pigment, a substance selected from the group consisting of oil and fat and Waxy compound Which is immiscible for said vinyl resin, nonvolatile and non-drying, and a dispersant for said pigment,

applying a covering layer on the record pigment layer by applying a covering solution and evaporating a solvent contained therein, said covering solution being prepared by dissolving and dispersing in a solvent materials including a substance selected from the group consisting of cellulose derivatives, 2. pigment selected from the group consisting of a white pigment and a pigment of the same color as said paper, and a waxy compound, said solvent being a non-solvent for the vinyl resin and the pigment forming said underlying record pigment layer but a solvent for said synthetic resin and said waxy compound, applying a microscopically discrete transparent adhesive layer on the covering layer by applying an adhesive providing solution and evaporating a solvent contained therein, said adhesive-providing solution being prepared by dissolving and dispersing low molecular polyethylene, a Waxy compound selected from the group consisting of stearic acid and paratfin in a mixed solvent of aromatic hydrocarbons and aliphatic hydrocarbons, wherein the ink composition of said microscopically discrete record pigment layer comprises:

Parts by weight Record pigment Carbon black i 00. 1

Oil and fat or waxy Hardened oiL 0.2

compound Dispersant Polyvinylpyrrolidone 0.2

Synthetic resin Vinyl chloridel vinyl acetate copolymer: 0.

Solvent Methyl ethyl ketone 2. 0

Toluene 7. 0

and wherein the ink composition of said microscopically discrete covering layer comprises:

and wherein the ink composition of said microscopically discrete adhesive layer comprises:

Parts by weight Low molecular weight poly- 2. 0

ethylene. Waxy compound Paraffin 0. 2

Hydrocarbon solvent Toluene 25. 0 Petroleum benzine- 10. 0

References Cited UNITED STATES PATENTS 2,188,590 1/1940 Bjorksten et a1 ..l 11736.4 2,729,575 1/ 6 Newman 117-3 6.4 3,256,107 6/1966 Strauss '11736.4 3,257,942 6/1966 Ri-tzerfeld et a1 11736.4 3,340,086 9/1967 Groak ...1... 117-367 3,458,339 7/1969 Newman et al. 11736.4

MURRAY KATZ, Primary Examiner US. Cl. XIR- @2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORhneFION Patent No. 3,539,376 Dated November 10, 1970 Invent0r s Sumio Otani and Taiji Shimada It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In claim 1, line 4, "colution" should be -solution- In claim 2, line 7 after "a pigment", please insert -as record pigment--.

Signed and sealed this 22nd day of June 1 971 (SEAL) Atte st:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLEH, JR. Atte sting Officer Commissioner of Patents 

